The present invention relates to processes for hydroxylating olefins in the presence of a specifically defined catalyst and oxidant combination.
Processes for the production of glycols such as ethylene glycol, from olefins are well known in the art.
For example, it is well known from the technical literature and patents that olefins can be effectively oxidized with a strong oxidizing agent in the presence of catalytic amounts of specific osmium oxide containing compounds, particularly osmium tetroxide, e.g., to their corresponding glycols.
The patent literature directed to osmium containing hydroxylation catalysts describes various osmium oxides used in conjunction with specific oxidants. The primary oxide catalyst employed in these patents is OsO.sub.4, a highly volatile (B.P. 130.degree. C.) and toxic substance. Ordinarily, the toxic nature of OsO.sub.4 alone, while troublesome to some extent, could be dealt with by resonably economic precautions. However, the combined properties of high volatility and toxicity human tolerance is 0.002 mg/m.sup.3 of air) render this compound extremely dangerous necessitating large capital expenditures in plant safety equipment and design if one attempts to commercialize a process employing this compound as a catalyst. It is for this reason that commercialization of OsO.sub.4 based plants has infrequently occurred in the past, if at all. If commercialization is attempted, the aforedescribed capital investment in safety equipment must reduce the profit margin on the products made by these processes.
Accordingly, it would be of extreme economic significance if alternative osmium catalysts could be indentified which possess the property of low volatility and/or low toxicity (in relation to OsO.sub.4), together with processes for using the same to achieve glycol product selectivity and yield comparable to or better than the conventional OsO.sub.4 catalyst.
Norton, U.S. Pat. No. 3,335,174, is directed to the use of Group Vb, VI-b, and VII metal halides and oxyhalides (e.g., OsCl.sub.3) as hydroxylation and esterification catalysts in conjunction with aqueous H.sub.2 O.sub.2 as an oxidant. However, the process for using this catalyst requires the presence of lower aliphatic hydrocarbon acids such as formic, acetic and propionic acid as solvents. Under these conditions the reaction times vary from 1/2 to 4 hours, but at the shorter reaction times it is disclosed that substantial amounts of epoxide result thereby indicating that the reaction proceeds via the peracid route wherein epoxide intermediates are hydrolyzed to corresponding diols. When the equivalent of Example 2 of this patent was conducted (see Comparative Example 1 herein) the conversion of hydrogen peroxide was found to be 10%, the selectivity to diol was 10%, the selectivity to diacetate was 20%, and the diol yield was 1%. Clearly, Norton is attempting to utilize the peracid route of olefin oxidations and osmium halide as, in practical effect an intermediate epoxidation catalyst. Unfortunately, however, Norton cannot control the subsequent esterification of epoxide-derived diol and hence more ester forms than diol. Thus, among the major disadvantages of the process described in this patent are the low selectivities to diol, the corrosiveness of metal halides in the presence of glacial acids such as acetic acid, and the use of hydrogen peroxide (an expensive reagent) as the oxidant.
In an extensive review article by Martin Schroder, "Osmium Tetraoxide Cis Hydroxylation of Unsaturated Substrates" Chemical Reviews, Vol. 80, pp. 187-213 (1980) (hereinafter Schroder), the comment is made at page 203 thereof in interpreting Norton that osmium trichloride behaves as a nonvolatile source of osmium tetraoxide in the process of Norton, the tetraoxide being generated in-situ by hydrogen peroxide oxidation. This observation of Schroder, and others (see also Br. Pat. Spec. No. 1,324,763, p.3, col.2, lines 55 et.seq.), is unsupported by experimental data. Moreover, experimental data has been supplied herein to show that osmium-halides are not converted to OsO.sub.4 in the presently claimed invention and it is doubted that the same occurs in Norton.
In contrast to the peracid route to olefin hydroxylation and esterification utilized in Norton, it is well known from the technical literature, that olefins can be oxidized directly to their corresponding diols, stoichiometrically or catalytically, with osmium oxide compounds, particularly osmium tetroxide. The direct hydroxylation of olefins is distinctively different from the peracid route of Norton since it does not form an epoxide intermediate.
The non-catalytic, i.e. stoichiometric, cis-hydroxylation of alkenes with OsO.sub.4 has been conventionally characterized as taking place via the formation, with the alkene, of an osmium (VI) intermediate ester complex. [See for example, Schroder pp. 187-213.]
To convert the non-catalytically prepared osmium (VI) ester complex intermediate to the diol, the intermediate can be hydrolyzed reductively. Reductive hydrolysis is conventionally carried out by using alkali metal sulfites, bisulfites, lithium aluminum hydride, or hydrogen sulfide to yield the corresponding cis-diols together with lower valence forms of osmium which are removed by filtration.
In contrast to the stoichiometric non-catalytic mode of cis-hydroxylation with OsO.sub.4, the catalytic mode employs a secondary oxidant to oxidatively hydrolyze the intermediate Osmium (VI) ester and regenerate the OsO.sub.4 which can undergo further reduction by the substrate olefin. A variety of oxidants have been employed in conjunction with the use of OsO.sub.4 in the catalytic mode such as H.sub.2 O.sub.2, t-butyl hydroperoxide and oxygen.
The use of oxygen as oxidant in such osmium oxide based catalytic systems has encountered considerable difficulty due to the appreciable overoxidation of the products, particularly at elevated temperatures (e.g. 70.degree.-80.degree. C.), leading to the formation of keto or acid products. However, if the reaction temperature is lowered to reduce overoxidation, the reaction rate is so low that yields of cis-diol are drastically reduced. An additional disadvantage of the use of oxygen oxidant is that the reaction is pH dependent (See Schroder, page 210, col. 1).
The poor performance of oxygen based osmium catalyzed olefin hydroxylation systems is unfortunate, since such systems have inherent advantages over organic hydroperoxide based systems. For example, hydroxylation systems employing organohydroperoxide oxidants result in the conversion of the organohydroperoxide to its corresponding alcohol during the formation of the desired olefin derived diol. Thus, for example, t-butyl hydroperoxide is converted to t-butyl alcohol. The commercial attractiveness of such processes is dependent on the ability to use or sell the organic alcohol co-product in addition to the diol. Given the fluctuation in economic conditions, however, it may be difficult to dispose of large quantities of these organic alcohol co-products in an economically attractive manner. In any event, it can be troublesome, when the quantity of one product, selected on the basis of marketing possibilities for a given period, necessarily determines the quantity of some other product which may be smaller or larger than desirable in view of changing marketing requirements within that same period. It can, therefore, under certain circumstances be considered as a disadvantage of the aforenoted organohydroperoxide based processes that such large quantities of organic alcohols are formed as co-products, even though under other circumstances the formation of two products may well be found acceptable.
In contrast, oxygen based hydroxylation systems do not produce an oxidant derived alcohol co-product that must be disposed of, which can be a significant advantage.
The search has, therefore, continued for ways of improving the rate and/or selectivity of osmium catalyzed oxygen based processes for hydroxylating olefins.
One step in this direction is disclosed in commonly assigned U.S. patent application Ser. No. 310,097, filed Oct. 9, 1981, by R. Austin and R. Michaelson, the inventors herein. This application describes a process for the hydroxylation of olefins using oxygen as an oxidant, a catalytically active metal oxide catalyst such as OsO.sub.4, and at least one transition metal salt co-catalyst such as copper bromide. This process can also be conducted in the optional presence of a second co-catalyst such as alkali metal halides. While the use of the transition metal co-catalyst substantially improves the reaction rate and/or selectivity of the hydroxylation reaction, the search has continued for ways to alleviate the aforedescribed disadvantages of osmium oxides.
Commonly assigned U.S. Pat. No. 4,314,088 issued Feb. 2, 1982 and a continuation-in-part thereof, namely, U.S. patent application Ser. No. 310,099 filed Oct. 9, 1981 by R. Austin and R. Michaelson collectively, disclose the use of various halide containing co-catalysts in conjunction with osmium tetroxide catalyst and organohydroperoxide oxidants to hydroxylate olefins. The halide containing co-catalysts include alkali and alkaline earth metal halides, hydrogen-halides, quarternary hydrocarbyl phosphonium halides, halogens, and transition metal halides. The use of oxygen as an oxidant either alone or in conjunction with a transition metal co-catalyst is not disclosed.
U.S. patent application Ser. No. 399,270 filed July 19, 1982, by R. Austin and R. Michaelson is directed to a process for hydroxylating olefins in the presence of an organohydroperoxide oxidant, an osmium containing catalyst and an organic halogenated hydrocarbon co-catalyst.
Commonly assigned U.S. patent application Ser. No. 394,414, filed July 1, 1982 by R. Michaelson and R. Austin, is directed to the use of carboxylate salts as co-catalysts for use in conjunction with osmium oxides as a catalyst and organohydroperoxide as oxidant to hydroxylate olefins.
Commonly assigned U.S. patent application Ser. No. 397,997 filed July 14, 1982, by R. Michaelson, R. Austin, and D. White is directed to a process for hydroxylating olefins in the presence of a supported osmium containing catalyst (e.g., supported OsBr.sub.3), optional co-catalysts and an oxidant selected from hydrogen peroxide, organohydroperoxides and oxygen.
Commonly assigned U.S. patent application Ser. No. 420,137 filed Sept. 20, 1982 by R. Michaelson, R. Austin, and D. White is directed to a process for hydroxylating olefins in the presence of an osmium carbonyl catalyst, optional co-catalysts and an oxidant selected from hydrogen peroxide, organohydroperoxide, and oxygen.
Commonly assigned U.S. patent application Ser. No. 440,964 filed Nov. 12, 1982 by R. Michaelson, R. Austin, and D. White is directed to a process for hydroxylating olefins in the presence of an osmium oxide catalyst, optional co-catalysts and sodium hydroxide as a promoter.
U.S. Pat. No. 2,414,385 discloses the use of hydrogen peroxide and a catalytically active oxide, such as osmium tetroxide, dissolved in an essentially anhydrous, non-alkaline, inert, preferably organic, solvent, to convert, by oxidation, unsaturated organic compounds to useful oxygenated products such as glycols, phenols, aldehydes, ketones, quinones and organic acids. The formation of glycols is achieved by conducting the reaction at temperatures of between several degrees below 0.degree. C. and 21.degree. C. Such low reaction temperatures drastically, and disadvantageously, reduce the reaction rate to commercially unacceptable levels. At temperatures greater than 21.degree. C., the formation of aldehydes, ketones, and acids is favored.
U.S. Pat. No. 2,773,101 discloses a method for recovering an osmium containing catalyst such as osmium tetroxide, by converting it to the non-volatile osmium dioxide form, distilling the hydroxylation product, re-oxidizing the osmium dioxide to the volatile osmium tetroxide, and then recovering the same by distillation. Suitable oxidizing agents used to re-oxidize the osmium dioxide, include inorganic peroxides such as hydrogen peroxide, sodium peroxide, barium peroxide; organic peroxides, such as t-butyl peroxide or hydroperoxide, benzoyl peroxide; as well as other oxidizing agents such as oxygen; perchlorates, nitric acid, chlorine water and the like. As with other methods of the prior art, the above process yields undesirable by-products (See Col. 1, Line 55) thus reducing the selectivity of the process.
British Patent Specification No. 1,028,940 is directed to a process for regenerating osmium tetroxide from reduced osmium tetroxide by treatment of the latter with molecular oxygen in an aqueous alkaline solution. More specifically, it is disclosed that when osmium tetroxide is used by itself as an oxidizing agent, or as a catalyst in conjunction with other oxidizing agents, to oxidize hydrocarbons the osmium tetroxide becomes reduced, and in its reduced form is less active than osmium tetroxide itself. Consequently, by conducting the oxidation reaction in the presence of an alkaline medium and supplying oxygen to the medium throughout the process, the osmium tetroxide is maintained in a high state of activity. The oxidation products disclosed include not only ethylene glycol from ethylene but also organic acids from such compounds as vicinal glycols, olefins, ketones and alcohols.
U.S. Pat. No. 4,255,596 is directed to a process for preparing ethylene glycol in a homogeneous single-phase reaction medium using ethylbenzene hydroperoxide as the oxidizing agent dissolved in ethylbenzene and osmium tetroxide as the catalyst. The pH of the reaction medium is maintained at about 14 by the presence of tetraalkylammonium hydroxide. A small amount of water can dissolve beneficially in the medium to reduce by-product formation and improve selectivity to the glycol.
U.S. Pat. No. 4,049,724 describes the preparation of glycols from alkenes and from unsaturated alcohols in an aqueous system using osmium tetroxide and specifying stable and water-soluble aliphatic hydroperoxides, such as t-butyl hydroperoxide, while a critical pH of 8 to 12 is maintained by a suitable combination of alkali metal buffering compounds. The preparation of propylene glycol utilizing t-butyl hydroperoxide is exemplified in the patent at a selectivity based on the hydroperoxide of 45%.
Japanese Patent Application No. Sho 54-145604, published Nov. 14, 1979, is directed to a process for hydroxylating olefins in the presence of OsO.sub.4, a quaternary ammonium salt such as tetraethylammonium bromide, and a peroxide including organoperoxides and H.sub.2 O.sub.2 as the oxidant.
See also: U.S. Pat. No. 3,317,592 (discloses production of acids and glycols using oxygen as oxidant, OsO.sub.4 as catalyst at pH 8 to 10); U.S. Pat. No. 3,488,394 (discloses hydroxylation of olefins by reacting olefin and hypochlorite in the presence of OsO.sub.4); U.S. Pat. No. 3,846,478 (discloses reaction of hypochlorite and olefin in an aqueous medium and in the presence of OsO.sub.4 catalyst to hydroxylate the olefin); U.S. Pat. No. 3,928,473 (hydroxylation of olefins to glycols with O.sub.2 oxidant, octavalent osmium catalyst (e.g. OsO.sub.4), and borates as promoter); U.S. Pat. No. 3,931,342 (discloses a process for recovering glycols from an aqueous solution containing alkali metal borate and osmium compounds (e.g. OsO.sub.4)); U.S. Pat. No. 3,953,305 (discloses use of OsO.sub.4 catalyst for hydroxylating olefins which is regenerated by oxidizing hexavalent osmium with hexavalent chromium and electro-chemically regenerating hexavalent chromium); U.S. Pat. No. 4,203,926 (discloses ethylbenzene hydroperoxide as oxidant used in two-phase system to hydroxylate olefins in presence of OsO.sub.4 and cesium, rubidium and potassium hydroxides); U.S. Pat. No. 4,217,291 (discloses the oxidation of Osmium (III) or (IV) in an ionic complex with oxygen and an alkali metal, ammonium, or tetra(lower)alkylammonium cation to a valency of greater than +5 and organohydroperoxides); U.S. Pat. No. 4,299,601 (discloses the use of cesium, rubidium, and potassium hydroxides as promoters for OsO.sub.4 catalyst and t-butyl hydroperoxide oxidant for hydroxylating olefins); U.S. Pat. No. 4,280,924 (discloses a process for regenerating perosmate catalyst, e.g., cesium, rubidium and potassium perosmate); and European Patent Application No. 0004725 (discloses production of glycols from olefins using Cu or Fe ions, and ions of Br and I, and O.sub.2, but in the absence of osmium.
None of the aforenoted patents disclose the use of osmium halides or oxy halides as catalysts for cis-hydroxylation reaction between olefins, and oxygen oxidants.
Accordingly, the search has continued for relatively non-volatile and/or relatively non-toxic osmium compounds capable of catalyzing such hydroxylation reactions between olefins and oxygen. The present invention is a result of this search.